NXP Semiconductors MC9S08LG16, Reference Manual

Page: 61 / 373

Chapter 4 Memory
MC9S08LG32 MCU Series, Rev. 5
Freescale Semiconductor 61
4.6.1 Features
Features of the flash memory include:
• Flash size
— MC9S08LG32: 32,768 bytes (16,384 bytes in Flash A, 16,384 bytes in Flash B)
— MC9S08LG16: 18,432 bytes (2,048 bytes in Flash A, 16,384 in Flash B)
• Single power supply program and erase
• Command interface for fast program and erase operation
• Up to 100,000 program/erase cycles at typical voltage and temperature
• Flexible block protection
• Security feature for flash and RAM
• Auto power-down for low-frequency read accesses
4.6.2 Program and Erase Times
Before any program or erase command can be accepted, the flash clock divider register (FCDIV) must be
written to set the internal clock for the flash module to a frequency (f
FCLK
) between 150 kHz and 200 kHz
(see Section 4.8.1, “Flash Clock Divider Register (FCDIV) ”). This register can be written only once, so
normally this write is performed during reset initialization. FCDIV cannot be written if the access error
flag, FACCERR in FSTAT, is set. Ensure that FACCERR is not set before writing to the FCDIV register.
The command processor uses one period of the resulting clock (1/f
FCLK
) to time program and erase pulses.
An integer number of these timing pulses is used by the command processor to complete a program or
erase command.
Table 4-6 shows program and erase times. The bus clock frequency and FCDIV determine the frequency
of FCLK (f
FCLK
). The time for one cycle of FCLK is t
FCLK
= 1/f
FCLK
. The times are shown as a number
of cycles of FCLK and as an absolute time for the case where t
FCLK
= 5
μ
s. Program and erase times
shown include overhead for the command state machine and enabling and disabling of program and erase
voltages.
Table 4-6. Program and Erase Times
Parameter Cycles of FCLK Time if FCLK = 200 kHz
Byte program 9 45
μ
s
Byte program (burst) 4 20
μ
s
1
1
Excluding start/end overhead
Page erase 4000 20 ms
Mass erase 20,000 100 ms